Known as 'Handsome Harry,' he was an associate and a bank-robbing mentor of John Dillinger.
He met Dillinger when the latter serving a 10-20 year sentence for robbery, and Pierpont was already a hard criminal with a long rap sheet.
He taught Dillinger to be methodical about robberies: planning the robberies, casing the joint, and arranging - even practicing - the getaway routes.
He was born in Muncie, Indiana.
He was played by Geoffrey Lewis in the 1973 film Dillinger.